B & S 18.5hp twin problems , please help !!!

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Old 05-18-09, 08:56 PM
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B & S 18.5hp twin problems , please help !!!

OK , I have a MTD with a briggs 18.5 hp twin engine which runs great with the clutch/brake in , I can engage the blades while the clutch/brake is in and still runs fine. As soon as I left off the brake/clutch with it in gear or out of gear , it spits and sputters and won't stay running. As soon as I press in the brake/clutch it's back to running like nothing is wrong. I have replaced all the obvious stuff (air and fuel filter and plugs.) Could it be that I have some old gas in it ? Wouldn't it run bad at idle and with the load of the blades engaged ?

Here is the #'s on my engine ....

Model #- 42A707

Type #- 123801

Code #-9602085A

Any help would be greatly appreciated because i'm clueless and I don't really have the money to take it to a repair shop.

Thank you ,
Mark
 
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Old 05-18-09, 09:12 PM
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With the engine OFF & the spark plugs un-plugged, Try to turn all the idlers & pulleys assoicated with the drive for the deck to make sure nothing is siezing up.. .If all looks good, Check the seat switch, as that's a common problem.. Does It drive & move O.K. without the deck engaged??? (wondering about a lean carb issue here)The Pros may need the #'s from the mower as well as the make of it to really get into it,,, Good Luck,, Roger
 
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Old 05-18-09, 09:18 PM
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That's an odd problem. I'm wondering if there is a problem with the clutch switch, or if it's running on one cylinder, or if the brake is stuck?
 
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Old 05-18-09, 09:20 PM
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Originally Posted by hopkinsr2 View Post
With the engine OFF & the spark plugs un-plugged, Try to turn all the idlers & pulleys assoicated with the drive for the deck to make sure nothing is siezing up.. .If all looks good, Check the seat switch, as that's a common problem.. Does It drive & move O.K. without the deck engaged??? (wondering about a lean carb issue here)The Pros may need the #'s from the mower as well as the make of it to really get into it,,, Good Luck,, Roger
With the blades engaged sitting still with the clutch/brake engaged , it runs perfect and as soon as I left off the clutch the slightest bit, it starts spitting and popping ....
 
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Old 05-18-09, 09:23 PM
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Originally Posted by cheese View Post
That's an odd problem. I'm wondering if there is a problem with the clutch switch, or if it's running on one cylinder, or if the brake is stuck?
I'm clueless. Doesn't make sense to run good at idle with blades engaged and soon as I try and take off it starts acting up.

Should I check the plugs ? And if so, what should I look for exactly ? Could it be the coil ?
 
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Old 05-18-09, 09:30 PM
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Ok, you said in the last post that letting off the clutch even the slightest bit does it. This would lead me to think it is in fact an electrical problem related to either the clutch switch malfunctioning somehow or a wire that has chaffed against a component that moves when you press/release the clutch and is shorting. I don't think there is a problem with the engine itself.
 
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Old 05-18-09, 09:34 PM
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Originally Posted by cheese View Post
Ok, you said in the last post that letting off the clutch even the slightest bit does it. This would lead me to think it is in fact an electrical problem related to either the clutch switch malfunctioning somehow or a wire that has chaffed against a component that moves when you press/release the clutch and is shorting. I don't think there is a problem with the engine itself.

this past weekend I had it out again trying to get it working and it's very frustrating. I know a little bit about engines as long as it's on the outside . As far as what you mentioned here, I don't have the foggiest idea. Do you think that 1 of these problems would cause it to run so bad that the engine would act like it's not getting enough or too much gas ?
 
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Old 05-18-09, 09:37 PM
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Now that you mention it, it does seem that the clutch does travel back towards me further then normal. If I remember correctly when it was running right , it would travel maybe 4 inches back at the most and now it seems to be traveling 7 or 8 inches. Could that be the problem ?
 
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Old 05-18-09, 09:41 PM
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Sorry, I read you're first post wrong.. (I'm not the sharpest tac in the bulletin board.. LOL) If you leave the blades disengaged, can you drive it?? Some of these have a switch that will kill the engine if you engage reverse gear with the blades engaged... Maybe check that switch to see if it's damaged ?? Roger
 
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Old 05-18-09, 09:55 PM
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Originally Posted by hopkinsr2 View Post
Sorry, I read you're first post wrong.. (I'm not the sharpest tac in the bulletin board.. LOL) If you leave the blades disengaged, can you drive it?? Some of these have a switch that will kill the engine if you engage reverse gear with the blades engaged... Maybe check that switch to see if it's damaged ?? Roger
With the blades disengaged it does the same thing. With or without the blades engaged it still does the same thing. I was just putting emphasis on the blades being engaged with the clutch in produced no engine problems until I tried releasing the clutch. Should I run down to the shed and get the model # of the tractor ? Its an MTD but I dont have the #'s on me.
 
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Old 05-18-09, 10:15 PM
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Press the clutch a little at a time while trying to start it. See at what point the switch in the clutch allows the engine to start. Then with the engine running, start letting off the clutch and see if it makes the engine mess up at the same spot in clutch travel. If so, this doesn't prove it's a switch problem, but it supports the theory.
 
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